/* vim: set tabstop=4 softtabstop=4 shiftwidth=4 noexpandtab: */ /**

* Backbone-relational.js 0.10.0
* (c) 2011-2014 Paul Uithol and contributors (https://github.com/PaulUithol/Backbone-relational/graphs/contributors)
*
* Backbone-relational may be freely distributed under the MIT license; see the accompanying LICENSE.txt.
* For details and documentation: https://github.com/PaulUithol/Backbone-relational.
* Depends on Backbone (and thus on Underscore as well): https://github.com/documentcloud/backbone.
*
* Example:
*
       Zoo = Backbone.RelationalModel.extend({
               relations: [ {
                       type: Backbone.HasMany,
                       key: 'animals',
                       relatedModel: 'Animal',
                       reverseRelation: {
                               key: 'livesIn',
                               includeInJSON: 'id'
                               // 'relatedModel' is automatically set to 'Zoo'; the 'relationType' to 'HasOne'.
                       }
               } ],

               toString: function() {
                       return this.get( 'name' );
               }
       });

       Animal = Backbone.RelationalModel.extend({
               toString: function() {
                       return this.get( 'species' );
               }
       });

       // Creating the zoo will give it a collection with one animal in it: the monkey.
       // The animal created after that has a relation `livesIn` that points to the zoo it's currently associated with.
       // If you instantiate (or fetch) the zebra later, it will automatically be added.

       var zoo = new Zoo({
               name: 'Artis',
               animals: [ { id: 'monkey-1', species: 'Chimp' }, 'lion-1', 'zebra-1' ]
       });

       var lion = new Animal( { id: 'lion-1', species: 'Lion' } ),
               monkey = zoo.get( 'animals' ).first(),
               sameZoo = lion.get( 'livesIn' );
*/

( function( root, factory ) {

// Set up Backbone-relational for the environment. Start with AMD.
if ( typeof define === 'function' && define.amd ) {
        define( [ 'exports', 'backbone', 'underscore' ], factory );
}
// Next for Node.js or CommonJS.
else if ( typeof exports !== 'undefined' ) {
        factory( exports, require( 'backbone' ), require( 'underscore' ) );
}
// Finally, as a browser global. Use `root` here as it references `window`.
else {
        factory( root, root.Backbone, root._ );
}

}( this, function( exports, Backbone, _ ) {

"use strict";

Backbone.Relational = {
        showWarnings: true
};

/**
 * Semaphore mixin; can be used as both binary and counting.
 **/
Backbone.Semaphore = {
        _permitsAvailable: null,
        _permitsUsed: 0,

        acquire: function() {
                if ( this._permitsAvailable && this._permitsUsed >= this._permitsAvailable ) {
                        throw new Error( 'Max permits acquired' );
                }
                else {
                        this._permitsUsed++;
                }
        },

        release: function() {
                if ( this._permitsUsed === 0 ) {
                        throw new Error( 'All permits released' );
                }
                else {
                        this._permitsUsed--;
                }
        },

        isLocked: function() {
                return this._permitsUsed > 0;
        },

        setAvailablePermits: function( amount ) {
                if ( this._permitsUsed > amount ) {
                        throw new Error( 'Available permits cannot be less than used permits' );
                }
                this._permitsAvailable = amount;
        }
};

/**
 * A BlockingQueue that accumulates items while blocked (via 'block'),
 * and processes them when unblocked (via 'unblock').
 * Process can also be called manually (via 'process').
 */
Backbone.BlockingQueue = function() {
        this._queue = [];
};
_.extend( Backbone.BlockingQueue.prototype, Backbone.Semaphore, {
        _queue: null,

        add: function( func ) {
                if ( this.isBlocked() ) {
                        this._queue.push( func );
                }
                else {
                        func();
                }
        },

        // Some of the queued events may trigger other blocking events. By
        // copying the queue here it allows queued events to process closer to
        // the natural order.
        //
        // queue events [ 'A', 'B', 'C' ]
        // A handler of 'B' triggers 'D' and 'E'
        // By copying `this._queue` this executes:
        // [ 'A', 'B', 'D', 'E', 'C' ]
        // The same order the would have executed if they didn't have to be
        // delayed and queued.
        process: function() {
                var queue = this._queue;
                this._queue = [];
                while ( queue && queue.length ) {
                        queue.shift()();
                }
        },

        block: function() {
                this.acquire();
        },

        unblock: function() {
                this.release();
                if ( !this.isBlocked() ) {
                        this.process();
                }
        },

        isBlocked: function() {
                return this.isLocked();
        }
});
/**
 * Global event queue. Accumulates external events ('add:<key>', 'remove:<key>' and 'change:<key>')
 * until the top-level object is fully initialized (see 'Backbone.RelationalModel').
 */
Backbone.Relational.eventQueue = new Backbone.BlockingQueue();

/**
 * Backbone.Store keeps track of all created (and destruction of) Backbone.RelationalModel.
 * Handles lookup for relations.
 */
Backbone.Store = function() {
        this._collections = [];
        this._reverseRelations = [];
        this._orphanRelations = [];
        this._subModels = [];
        this._modelScopes = [ exports ];
};
_.extend( Backbone.Store.prototype, Backbone.Events, {
        /**
         * Create a new `Relation`.
         * @param {Backbone.RelationalModel} [model]
         * @param {Object} relation
         * @param {Object} [options]
         */
        initializeRelation: function( model, relation, options ) {
                var type = !_.isString( relation.type ) ? relation.type : Backbone[ relation.type ] || this.getObjectByName( relation.type );
                if ( type && type.prototype instanceof Backbone.Relation ) {
                        var rel = new type( model, relation, options ); // Also pushes the new Relation into `model._relations`
                }
                else {
                        Backbone.Relational.showWarnings && typeof console !== 'undefined' && console.warn( 'Relation=%o; missing or invalid relation type!', relation );
                }
        },

        /**
         * Add a scope for `getObjectByName` to look for model types by name.
         * @param {Object} scope
         */
        addModelScope: function( scope ) {
                this._modelScopes.push( scope );
        },

        /**
         * Remove a scope.
         * @param {Object} scope
         */
        removeModelScope: function( scope ) {
                this._modelScopes = _.without( this._modelScopes, scope );
        },

        /**
         * Add a set of subModelTypes to the store, that can be used to resolve the '_superModel'
         * for a model later in 'setupSuperModel'.
         *
         * @param {Backbone.RelationalModel} subModelTypes
         * @param {Backbone.RelationalModel} superModelType
         */
        addSubModels: function( subModelTypes, superModelType ) {
                this._subModels.push({
                        'superModelType': superModelType,
                        'subModels': subModelTypes
                });
        },

        /**
         * Check if the given modelType is registered as another model's subModel. If so, add it to the super model's
         * '_subModels', and set the modelType's '_superModel', '_subModelTypeName', and '_subModelTypeAttribute'.
         *
         * @param {Backbone.RelationalModel} modelType
         */
        setupSuperModel: function( modelType ) {
                _.find( this._subModels, function( subModelDef ) {
                        return _.filter( subModelDef.subModels || [], function( subModelTypeName, typeValue ) {
                                var subModelType = this.getObjectByName( subModelTypeName );

                                if ( modelType === subModelType ) {
                                        // Set 'modelType' as a child of the found superModel
                                        subModelDef.superModelType._subModels[ typeValue ] = modelType;

                                        // Set '_superModel', '_subModelTypeValue', and '_subModelTypeAttribute' on 'modelType'.
                                        modelType._superModel = subModelDef.superModelType;
                                        modelType._subModelTypeValue = typeValue;
                                        modelType._subModelTypeAttribute = subModelDef.superModelType.prototype.subModelTypeAttribute;
                                        return true;
                                }
                        }, this ).length;
                }, this );
        },

        /**
         * Add a reverse relation. Is added to the 'relations' property on model's prototype, and to
         * existing instances of 'model' in the store as well.
         * @param {Object} relation
         * @param {Backbone.RelationalModel} relation.model
         * @param {String} relation.type
         * @param {String} relation.key
         * @param {String|Object} relation.relatedModel
         */
        addReverseRelation: function( relation ) {
                var exists = _.any( this._reverseRelations, function( rel ) {
                        return _.all( relation || [], function( val, key ) {
                                return val === rel[ key ];
                        });
                });

                if ( !exists && relation.model && relation.type ) {
                        this._reverseRelations.push( relation );
                        this._addRelation( relation.model, relation );
                        this.retroFitRelation( relation );
                }
        },

        /**
         * Deposit a `relation` for which the `relatedModel` can't be resolved at the moment.
         *
         * @param {Object} relation
         */
        addOrphanRelation: function( relation ) {
                var exists = _.any( this._orphanRelations, function( rel ) {
                        return _.all( relation || [], function( val, key ) {
                                return val === rel[ key ];
                        });
                });

                if ( !exists && relation.model && relation.type ) {
                        this._orphanRelations.push( relation );
                }
        },

        /**
         * Try to initialize any `_orphanRelation`s
         */
        processOrphanRelations: function() {
                // Make sure to operate on a copy since we're removing while iterating
                _.each( this._orphanRelations.slice( 0 ), function( rel ) {
                        var relatedModel = Backbone.Relational.store.getObjectByName( rel.relatedModel );
                        if ( relatedModel ) {
                                this.initializeRelation( null, rel );
                                this._orphanRelations = _.without( this._orphanRelations, rel );
                        }
                }, this );
        },

        /**
         *
         * @param {Backbone.RelationalModel.constructor} type
         * @param {Object} relation
         * @private
         */
        _addRelation: function( type, relation ) {
                if ( !type.prototype.relations ) {
                        type.prototype.relations = [];
                }
                type.prototype.relations.push( relation );

                _.each( type._subModels || [], function( subModel ) {
                        this._addRelation( subModel, relation );
                }, this );
        },

        /**
         * Add a 'relation' to all existing instances of 'relation.model' in the store
         * @param {Object} relation
         */
        retroFitRelation: function( relation ) {
                var coll = this.getCollection( relation.model, false );
                coll && coll.each( function( model ) {
                        if ( !( model instanceof relation.model ) ) {
                                return;
                        }

                        var rel = new relation.type( model, relation );
                }, this );
        },

        /**
         * Find the Store's collection for a certain type of model.
         * @param {Backbone.RelationalModel} type
         * @param {Boolean} [create=true] Should a collection be created if none is found?
         * @return {Backbone.Collection} A collection if found (or applicable for 'model'), or null
         */
        getCollection: function( type, create ) {
                if ( type instanceof Backbone.RelationalModel ) {
                        type = type.constructor;
                }

                var rootModel = type;
                while ( rootModel._superModel ) {
                        rootModel = rootModel._superModel;
                }

                var coll = _.find( this._collections, function( item ) {
                        return item.model === rootModel;
                });

                if ( !coll && create !== false ) {
                        coll = this._createCollection( rootModel );
                }

                return coll;
        },

        /**
         * Find a model type on one of the modelScopes by name. Names are split on dots.
         * @param {String} name
         * @return {Object}
         */
        getObjectByName: function( name ) {
                var parts = name.split( '.' ),
                        type = null;

                _.find( this._modelScopes, function( scope ) {
                        type = _.reduce( parts || [], function( memo, val ) {
                                return memo ? memo[ val ] : undefined;
                        }, scope );

                        if ( type && type !== scope ) {
                                return true;
                        }
                }, this );

                return type;
        },

        _createCollection: function( type ) {
                var coll;

                // If 'type' is an instance, take its constructor
                if ( type instanceof Backbone.RelationalModel ) {
                        type = type.constructor;
                }

                // Type should inherit from Backbone.RelationalModel.
                if ( type.prototype instanceof Backbone.RelationalModel ) {
                        coll = new Backbone.Collection();
                        coll.model = type;

                        this._collections.push( coll );
                }

                return coll;
        },

        /**
         * Find the attribute that is to be used as the `id` on a given object
         * @param type
         * @param {String|Number|Object|Backbone.RelationalModel} item
         * @return {String|Number}
         */
        resolveIdForItem: function( type, item ) {
                var id = _.isString( item ) || _.isNumber( item ) ? item : null;

                if ( id === null ) {
                        if ( item instanceof Backbone.RelationalModel ) {
                                id = item.id;
                        }
                        else if ( _.isObject( item ) ) {
                                id = item[ type.prototype.idAttribute ];
                        }
                }

                // Make all falsy values `null` (except for 0, which could be an id.. see '/issues/179')
                if ( !id && id !== 0 ) {
                        id = null;
                }

                return id;
        },

        /**
         * Find a specific model of a certain `type` in the store
         * @param type
         * @param {String|Number|Object|Backbone.RelationalModel} item
         */
        find: function( type, item ) {
                var id = this.resolveIdForItem( type, item ),
                        coll = this.getCollection( type );

                // Because the found object could be of any of the type's superModel
                // types, only return it if it's actually of the type asked for.
                if ( coll ) {
                        var obj = coll.get( id );

                        if ( obj instanceof type ) {
                                return obj;
                        }
                }

                return null;
        },

        /**
         * Add a 'model' to its appropriate collection. Retain the original contents of 'model.collection'.
         * @param {Backbone.RelationalModel} model
         */
        register: function( model ) {
                var coll = this.getCollection( model );

                if ( coll ) {
                        var modelColl = model.collection;
                        coll.add( model );
                        model.collection = modelColl;
                }
        },

        /**
         * Check if the given model may use the given `id`
         * @param model
         * @param [id]
         */
        checkId: function( model, id ) {
                var coll = this.getCollection( model ),
                        duplicate = coll && coll.get( id );

                if ( duplicate && model !== duplicate ) {
                        if ( Backbone.Relational.showWarnings && typeof console !== 'undefined' ) {
                                console.warn( 'Duplicate id! Old RelationalModel=%o, new RelationalModel=%o', duplicate, model );
                        }

                        throw new Error( "Cannot instantiate more than one Backbone.RelationalModel with the same id per type!" );
                }
        },

        /**
         * Explicitly update a model's id in its store collection
         * @param {Backbone.RelationalModel} model
         */
        update: function( model ) {
                var coll = this.getCollection( model );

                // Register a model if it isn't yet (which happens if it was created without an id).
                if ( !coll.contains( model ) ) {
                        this.register( model );
                }

                // This triggers updating the lookup indices kept in a collection
                coll._onModelEvent( 'change:' + model.idAttribute, model, coll );

                // Trigger an event on model so related models (having the model's new id in their keyContents) can add it.
                model.trigger( 'relational:change:id', model, coll );
        },

        /**
         * Unregister from the store: a specific model, a collection, or a model type.
         * @param {Backbone.RelationalModel|Backbone.RelationalModel.constructor|Backbone.Collection} type
         */
        unregister: function( type ) {
                var coll,
                        models;

                if ( type instanceof Backbone.Model ) {
                        coll = this.getCollection( type );
                        models = [ type ];
                }
                else if ( type instanceof Backbone.Collection ) {
                        coll = this.getCollection( type.model );
                        models = _.clone( type.models );
                }
                else {
                        coll = this.getCollection( type );
                        models = _.clone( coll.models );
                }

                _.each( models, function( model ) {
                        this.stopListening( model );
                        _.invoke( model.getRelations(), 'stopListening' );
                }, this );

                // If we've unregistered an entire store collection, reset the collection (which is much faster).
                // Otherwise, remove each model one by one.
                if ( _.contains( this._collections, type ) ) {
                        coll.reset( [] );
                }
                else {
                        _.each( models, function( model ) {
                                if ( coll.get( model ) ) {
                                        coll.remove( model );
                                }
                                else {
                                        coll.trigger( 'relational:remove', model, coll );
                                }
                        }, this );
                }
        },

        /**
         * Reset the `store` to it's original state. The `reverseRelations` are kept though, since attempting to
         * re-initialize these on models would lead to a large amount of warnings.
         */
        reset: function() {
                this.stopListening();

                // Unregister each collection to remove event listeners
                _.each( this._collections, function( coll ) {
                        this.unregister( coll );
                }, this );

                this._collections = [];
                this._subModels = [];
                this._modelScopes = [ exports ];
        }
});
Backbone.Relational.store = new Backbone.Store();

/**
 * The main Relation class, from which 'HasOne' and 'HasMany' inherit. Internally, 'relational:<key>' events
 * are used to regulate addition and removal of models from relations.
 *
 * @param {Backbone.RelationalModel} [instance] Model that this relation is created for. If no model is supplied,
 *      Relation just tries to instantiate it's `reverseRelation` if specified, and bails out after that.
 * @param {Object} options
 * @param {string} options.key
 * @param {Backbone.RelationalModel.constructor} options.relatedModel
 * @param {Boolean|String} [options.includeInJSON=true] Serialize the given attribute for related model(s)' in toJSON, or just their ids.
 * @param {Boolean} [options.createModels=true] Create objects from the contents of keys if the object is not found in Backbone.store.
 * @param {Object} [options.reverseRelation] Specify a bi-directional relation. If provided, Relation will reciprocate
 *    the relation to the 'relatedModel'. Required and optional properties match 'options', except that it also needs
 *    {Backbone.Relation|String} type ('HasOne' or 'HasMany').
 * @param {Object} opts
 */
Backbone.Relation = function( instance, options, opts ) {
        this.instance = instance;
        // Make sure 'options' is sane, and fill with defaults from subclasses and this object's prototype
        options = _.isObject( options ) ? options : {};
        this.reverseRelation = _.defaults( options.reverseRelation || {}, this.options.reverseRelation );
        this.options = _.defaults( options, this.options, Backbone.Relation.prototype.options );

        this.reverseRelation.type = !_.isString( this.reverseRelation.type ) ? this.reverseRelation.type :
                Backbone[ this.reverseRelation.type ] || Backbone.Relational.store.getObjectByName( this.reverseRelation.type );

        this.key = this.options.key;
        this.keySource = this.options.keySource || this.key;
        this.keyDestination = this.options.keyDestination || this.keySource || this.key;

        this.model = this.options.model || this.instance.constructor;

        this.relatedModel = this.options.relatedModel;

        // No 'relatedModel' is interpreted as self-referential
        if ( _.isUndefined( this.relatedModel ) ) {
                this.relatedModel = this.model;
        }

        // Otherwise, try to resolve the given value to an object
        if ( _.isFunction( this.relatedModel ) && !( this.relatedModel.prototype instanceof Backbone.RelationalModel ) ) {
                this.relatedModel = _.result( this, 'relatedModel' );
        }
        if ( _.isString( this.relatedModel ) ) {
                this.relatedModel = Backbone.Relational.store.getObjectByName( this.relatedModel );
        }

        if ( !this.checkPreconditions() ) {
                return;
        }

        // Add the reverse relation on 'relatedModel' to the store's reverseRelations
        if ( !this.options.isAutoRelation && this.reverseRelation.type && this.reverseRelation.key ) {
                Backbone.Relational.store.addReverseRelation( _.defaults( {
                                isAutoRelation: true,
                                model: this.relatedModel,
                                relatedModel: this.model,
                                reverseRelation: this.options // current relation is the 'reverseRelation' for its own reverseRelation
                        },
                        this.reverseRelation // Take further properties from this.reverseRelation (type, key, etc.)
                ) );
        }

        if ( instance ) {
                var contentKey = this.keySource;
                if ( contentKey !== this.key && _.isObject( this.instance.get( this.key ) ) ) {
                        contentKey = this.key;
                }

                this.setKeyContents( this.instance.get( contentKey ) );
                this.relatedCollection = Backbone.Relational.store.getCollection( this.relatedModel );

                // Explicitly clear 'keySource', to prevent a leaky abstraction if 'keySource' differs from 'key'.
                if ( this.keySource !== this.key ) {
                        delete this.instance.attributes[ this.keySource ];
                }

                // Add this Relation to instance._relations
                this.instance._relations[ this.key ] = this;

                this.initialize( opts );

                if ( this.options.autoFetch ) {
                        this.instance.getAsync( this.key, _.isObject( this.options.autoFetch ) ? this.options.autoFetch : {} );
                }

                // When 'relatedModel' are created or destroyed, check if it affects this relation.
                this.listenTo( this.instance, 'destroy', this.destroy )
                        .listenTo( this.relatedCollection, 'relational:add relational:change:id', this.tryAddRelated )
                        .listenTo( this.relatedCollection, 'relational:remove', this.removeRelated );
        }
};
// Fix inheritance :\
Backbone.Relation.extend = Backbone.Model.extend;
// Set up all inheritable **Backbone.Relation** properties and methods.
_.extend( Backbone.Relation.prototype, Backbone.Events, Backbone.Semaphore, {
        options: {
                createModels: true,
                includeInJSON: true,
                isAutoRelation: false,
                autoFetch: false,
                parse: false
        },

        instance: null,
        key: null,
        keyContents: null,
        relatedModel: null,
        relatedCollection: null,
        reverseRelation: null,
        related: null,

        /**
         * Check several pre-conditions.
         * @return {Boolean} True if pre-conditions are satisfied, false if they're not.
         */
        checkPreconditions: function() {
                var i = this.instance,
                        k = this.key,
                        m = this.model,
                        rm = this.relatedModel,
                        warn = Backbone.Relational.showWarnings && typeof console !== 'undefined';

                if ( !m || !k || !rm ) {
                        warn && console.warn( 'Relation=%o: missing model, key or relatedModel (%o, %o, %o).', this, m, k, rm );
                        return false;
                }
                // Check if the type in 'model' inherits from Backbone.RelationalModel
                if ( !( m.prototype instanceof Backbone.RelationalModel ) ) {
                        warn && console.warn( 'Relation=%o: model does not inherit from Backbone.RelationalModel (%o).', this, i );
                        return false;
                }
                // Check if the type in 'relatedModel' inherits from Backbone.RelationalModel
                if ( !( rm.prototype instanceof Backbone.RelationalModel ) ) {
                        warn && console.warn( 'Relation=%o: relatedModel does not inherit from Backbone.RelationalModel (%o).', this, rm );
                        return false;
                }
                // Check if this is not a HasMany, and the reverse relation is HasMany as well
                if ( this instanceof Backbone.HasMany && this.reverseRelation.type === Backbone.HasMany ) {
                        warn && console.warn( 'Relation=%o: relation is a HasMany, and the reverseRelation is HasMany as well.', this );
                        return false;
                }
                // Check if we're not attempting to create a relationship on a `key` that's already used.
                if ( i && _.keys( i._relations ).length ) {
                        var existing = _.find( i._relations, function( rel ) {
                                return rel.key === k;
                        }, this );

                        if ( existing ) {
                                warn && console.warn( 'Cannot create relation=%o on %o for model=%o: already taken by relation=%o.',
                                        this, k, i, existing );
                                return false;
                        }
                }

                return true;
        },

        /**
         * Set the related model(s) for this relation
         * @param {Backbone.Model|Backbone.Collection} related
         */
        setRelated: function( related ) {
                this.related = related;
                this.instance.attributes[ this.key ] = related;
        },

        /**
         * Determine if a relation (on a different RelationalModel) is the reverse
         * relation of the current one.
         * @param {Backbone.Relation} relation
         * @return {Boolean}
         */
        _isReverseRelation: function( relation ) {
                return relation.instance instanceof this.relatedModel && this.reverseRelation.key === relation.key &&
                        this.key === relation.reverseRelation.key;
        },

        /**
         * Get the reverse relations (pointing back to 'this.key' on 'this.instance') for the currently related model(s).
         * @param {Backbone.RelationalModel} [model] Get the reverse relations for a specific model.
         *    If not specified, 'this.related' is used.
         * @return {Backbone.Relation[]}
         */
        getReverseRelations: function( model ) {
                var reverseRelations = [];
                // Iterate over 'model', 'this.related.models' (if this.related is a Backbone.Collection), or wrap 'this.related' in an array.
                var models = !_.isUndefined( model ) ? [ model ] : this.related && ( this.related.models || [ this.related ] ),
                        relations = null,
                        relation = null;

                for( var i = 0; i < ( models || [] ).length; i++ ) {
                        relations = models[ i ].getRelations() || [];

                        for( var j = 0; j < relations.length; j++ ) {
                                relation = relations[ j ];

                                if ( this._isReverseRelation( relation ) ) {
                                        reverseRelations.push( relation );
                                }
                        }
                }

                return reverseRelations;
        },

        /**
         * When `this.instance` is destroyed, cleanup our relations.
         * Get reverse relation, call removeRelated on each.
         */
        destroy: function() {
                this.stopListening();

                if ( this instanceof Backbone.HasOne ) {
                        this.setRelated( null );
                }
                else if ( this instanceof Backbone.HasMany ) {
                        this.setRelated( this._prepareCollection() );
                }

                _.each( this.getReverseRelations(), function( relation ) {
                        relation.removeRelated( this.instance );
                }, this );
        }
});

Backbone.HasOne = Backbone.Relation.extend({
        options: {
                reverseRelation: { type: 'HasMany' }
        },

        initialize: function( opts ) {
                this.listenTo( this.instance, 'relational:change:' + this.key, this.onChange );

                var related = this.findRelated( opts );
                this.setRelated( related );

                // Notify new 'related' object of the new relation.
                _.each( this.getReverseRelations(), function( relation ) {
                        relation.addRelated( this.instance, opts );
                }, this );
        },

        /**
         * Find related Models.
         * @param {Object} [options]
         * @return {Backbone.Model}
         */
        findRelated: function( options ) {
                var related = null;

                options = _.defaults( { parse: this.options.parse }, options );

                if ( this.keyContents instanceof this.relatedModel ) {
                        related = this.keyContents;
                }
                else if ( this.keyContents || this.keyContents === 0 ) { // since 0 can be a valid `id` as well
                        var opts = _.defaults( { create: this.options.createModels }, options );
                        related = this.relatedModel.findOrCreate( this.keyContents, opts );
                }

                // Nullify `keyId` if we have a related model; in case it was already part of the relation
                if ( related ) {
                        this.keyId = null;
                }

                return related;
        },

        /**
         * Normalize and reduce `keyContents` to an `id`, for easier comparison
         * @param {String|Number|Backbone.Model} keyContents
         */
        setKeyContents: function( keyContents ) {
                this.keyContents = keyContents;
                this.keyId = Backbone.Relational.store.resolveIdForItem( this.relatedModel, this.keyContents );
        },

        /**
         * Event handler for `change:<key>`.
         * If the key is changed, notify old & new reverse relations and initialize the new relation.
         */
        onChange: function( model, attr, options ) {
                // Don't accept recursive calls to onChange (like onChange->findRelated->findOrCreate->initializeRelations->addRelated->onChange)
                if ( this.isLocked() ) {
                        return;
                }
                this.acquire();
                options = options ? _.clone( options ) : {};

                // 'options.__related' is set by 'addRelated'/'removeRelated'. If it is set, the change
                // is the result of a call from a relation. If it's not, the change is the result of
                // a 'set' call on this.instance.
                var changed = _.isUndefined( options.__related ),
                        oldRelated = changed ? this.related : options.__related;

                if ( changed ) {
                        this.setKeyContents( attr );
                        var related = this.findRelated( options );
                        this.setRelated( related );
                }

                // Notify old 'related' object of the terminated relation
                if ( oldRelated && this.related !== oldRelated ) {
                        _.each( this.getReverseRelations( oldRelated ), function( relation ) {
                                relation.removeRelated( this.instance, null, options );
                        }, this );
                }

                // Notify new 'related' object of the new relation. Note we do re-apply even if this.related is oldRelated;
                // that can be necessary for bi-directional relations if 'this.instance' was created after 'this.related'.
                // In that case, 'this.instance' will already know 'this.related', but the reverse might not exist yet.
                _.each( this.getReverseRelations(), function( relation ) {
                        relation.addRelated( this.instance, options );
                }, this );

                // Fire the 'change:<key>' event if 'related' was updated
                if ( !options.silent && this.related !== oldRelated ) {
                        var dit = this;
                        this.changed = true;
                        Backbone.Relational.eventQueue.add( function() {
                                dit.instance.trigger( 'change:' + dit.key, dit.instance, dit.related, options, true );
                                dit.changed = false;
                        });
                }
                this.release();
        },

        /**
         * If a new 'this.relatedModel' appears in the 'store', try to match it to the last set 'keyContents'
         */
        tryAddRelated: function( model, coll, options ) {
                if ( ( this.keyId || this.keyId === 0 ) && model.id === this.keyId ) { // since 0 can be a valid `id` as well
                        this.addRelated( model, options );
                        this.keyId = null;
                }
        },

        addRelated: function( model, options ) {
                // Allow 'model' to set up its relations before proceeding.
                // (which can result in a call to 'addRelated' from a relation of 'model')
                var dit = this;
                model.queue( function() {
                        if ( model !== dit.related ) {
                                var oldRelated = dit.related || null;
                                dit.setRelated( model );
                                dit.onChange( dit.instance, model, _.defaults( { __related: oldRelated }, options ) );
                        }
                });
        },

        removeRelated: function( model, coll, options ) {
                if ( !this.related ) {
                        return;
                }

                if ( model === this.related ) {
                        var oldRelated = this.related || null;
                        this.setRelated( null );
                        this.onChange( this.instance, model, _.defaults( { __related: oldRelated }, options ) );
                }
        }
});

Backbone.HasMany = Backbone.Relation.extend({
        collectionType: null,

        options: {
                reverseRelation: { type: 'HasOne' },
                collectionType: Backbone.Collection,
                collectionKey: true,
                collectionOptions: {}
        },

        initialize: function( opts ) {
                this.listenTo( this.instance, 'relational:change:' + this.key, this.onChange );

                // Handle a custom 'collectionType'
                this.collectionType = this.options.collectionType;
                if ( _.isFunction( this.collectionType ) && this.collectionType !== Backbone.Collection && !( this.collectionType.prototype instanceof Backbone.Collection ) ) {
                        this.collectionType = _.result( this, 'collectionType' );
                }
                if ( _.isString( this.collectionType ) ) {
                        this.collectionType = Backbone.Relational.store.getObjectByName( this.collectionType );
                }
                if ( this.collectionType !== Backbone.Collection && !( this.collectionType.prototype instanceof Backbone.Collection ) ) {
                        throw new Error( '`collectionType` must inherit from Backbone.Collection' );
                }

                var related = this.findRelated( opts );
                this.setRelated( related );
        },

        /**
         * Bind events and setup collectionKeys for a collection that is to be used as the backing store for a HasMany.
         * If no 'collection' is supplied, a new collection will be created of the specified 'collectionType' option.
         * @param {Backbone.Collection} [collection]
         * @return {Backbone.Collection}
         */
        _prepareCollection: function( collection ) {
                if ( this.related ) {
                        this.stopListening( this.related );
                }

                if ( !collection || !( collection instanceof Backbone.Collection ) ) {
                        var options = _.isFunction( this.options.collectionOptions ) ?
                                this.options.collectionOptions( this.instance ) : this.options.collectionOptions;

                        collection = new this.collectionType( null, options );
                }

                collection.model = this.relatedModel;

                if ( this.options.collectionKey ) {
                        var key = this.options.collectionKey === true ? this.options.reverseRelation.key : this.options.collectionKey;

                        if ( collection[ key ] && collection[ key ] !== this.instance ) {
                                if ( Backbone.Relational.showWarnings && typeof console !== 'undefined' ) {
                                        console.warn( 'Relation=%o; collectionKey=%s already exists on collection=%o', this, key, this.options.collectionKey );
                                }
                        }
                        else if ( key ) {
                                collection[ key ] = this.instance;
                        }
                }

                this.listenTo( collection, 'relational:add', this.handleAddition )
                        .listenTo( collection, 'relational:remove', this.handleRemoval )
                        .listenTo( collection, 'relational:reset', this.handleReset );

                return collection;
        },

        /**
         * Find related Models.
         * @param {Object} [options]
         * @return {Backbone.Collection}
         */
        findRelated: function( options ) {
                var related = null;

                options = _.defaults( { parse: this.options.parse }, options );

                // Replace 'this.related' by 'this.keyContents' if it is a Backbone.Collection
                if ( this.keyContents instanceof Backbone.Collection ) {
                        this._prepareCollection( this.keyContents );
                        related = this.keyContents;
                }
                // Otherwise, 'this.keyContents' should be an array of related object ids.
                // Re-use the current 'this.related' if it is a Backbone.Collection; otherwise, create a new collection.
                else {
                        var toAdd = [];

                        _.each( this.keyContents, function( attributes ) {
                                var model = null;

                                if ( attributes instanceof this.relatedModel ) {
                                        model = attributes;
                                }
                                else {
                                        // If `merge` is true, update models here, instead of during update.
                                        model = ( _.isObject( attributes ) && options.parse && this.relatedModel.prototype.parse ) ?
                                                this.relatedModel.prototype.parse( _.clone( attributes ), options ) : attributes;
                                }

                                model && toAdd.push( model );
                        }, this );

                        if ( this.related instanceof Backbone.Collection ) {
                                related = this.related;
                        }
                        else {
                                related = this._prepareCollection();
                        }

                        // By now, `parse` will already have been executed just above for models if specified.
                        // Disable to prevent additional calls.
                        related.set( toAdd, _.defaults( { parse: false }, options ) );
                }

                // Remove entries from `keyIds` that were already part of the relation (and are thus 'unchanged')
                this.keyIds = _.difference( this.keyIds, _.pluck( related.models, 'id' ) );

                return related;
        },

        /**
         * Normalize and reduce `keyContents` to a list of `ids`, for easier comparison
         * @param {String|Number|String[]|Number[]|Backbone.Collection} keyContents
         */
        setKeyContents: function( keyContents ) {
                this.keyContents = keyContents instanceof Backbone.Collection ? keyContents : null;
                this.keyIds = [];

                if ( !this.keyContents && ( keyContents || keyContents === 0 ) ) { // since 0 can be a valid `id` as well
                        // Handle cases the an API/user supplies just an Object/id instead of an Array
                        this.keyContents = _.isArray( keyContents ) ? keyContents : [ keyContents ];

                        _.each( this.keyContents, function( item ) {
                                var itemId = Backbone.Relational.store.resolveIdForItem( this.relatedModel, item );
                                if ( itemId || itemId === 0 ) {
                                        this.keyIds.push( itemId );
                                }
                        }, this );
                }
        },

        /**
         * Event handler for `change:<key>`.
         * If the contents of the key are changed, notify old & new reverse relations and initialize the new relation.
         */
        onChange: function( model, attr, options ) {
                options = options ? _.clone( options ) : {};
                this.setKeyContents( attr );
                this.changed = false;

                var related = this.findRelated( options );
                this.setRelated( related );

                if ( !options.silent ) {
                        var dit = this;
                        Backbone.Relational.eventQueue.add( function() {
                                // The `changed` flag can be set in `handleAddition` or `handleRemoval`
                                if ( dit.changed ) {
                                        dit.instance.trigger( 'change:' + dit.key, dit.instance, dit.related, options, true );
                                        dit.changed = false;
                                }
                        });
                }
        },

        /**
         * When a model is added to a 'HasMany', trigger 'add' on 'this.instance' and notify reverse relations.
         * (should be 'HasOne', must set 'this.instance' as their related).
         */
        handleAddition: function( model, coll, options ) {
                //console.debug('handleAddition called; args=%o', arguments);
                options = options ? _.clone( options ) : {};
                this.changed = true;

                _.each( this.getReverseRelations( model ), function( relation ) {
                        relation.addRelated( this.instance, options );
                }, this );

                // Only trigger 'add' once the newly added model is initialized (so, has its relations set up)
                var dit = this;
                !options.silent && Backbone.Relational.eventQueue.add( function() {
                        dit.instance.trigger( 'add:' + dit.key, model, dit.related, options );
                });
        },

        /**
         * When a model is removed from a 'HasMany', trigger 'remove' on 'this.instance' and notify reverse relations.
         * (should be 'HasOne', which should be nullified)
         */
        handleRemoval: function( model, coll, options ) {
                //console.debug('handleRemoval called; args=%o', arguments);
                options = options ? _.clone( options ) : {};
                this.changed = true;

                _.each( this.getReverseRelations( model ), function( relation ) {
                        relation.removeRelated( this.instance, null, options );
                }, this );

                var dit = this;
                !options.silent && Backbone.Relational.eventQueue.add( function() {
                        dit.instance.trigger( 'remove:' + dit.key, model, dit.related, options );
                });
        },

        handleReset: function( coll, options ) {
                var dit = this;
                options = options ? _.clone( options ) : {};
                !options.silent && Backbone.Relational.eventQueue.add( function() {
                        dit.instance.trigger( 'reset:' + dit.key, dit.related, options );
                });
        },

        tryAddRelated: function( model, coll, options ) {
                var item = _.contains( this.keyIds, model.id );

                if ( item ) {
                        this.addRelated( model, options );
                        this.keyIds = _.without( this.keyIds, model.id );
                }
        },

        addRelated: function( model, options ) {
                // Allow 'model' to set up its relations before proceeding.
                // (which can result in a call to 'addRelated' from a relation of 'model')
                var dit = this;
                model.queue( function() {
                        if ( dit.related && !dit.related.get( model ) ) {
                                dit.related.add( model, _.defaults( { parse: false }, options ) );
                        }
                });
        },

        removeRelated: function( model, coll, options ) {
                if ( this.related.get( model ) ) {
                        this.related.remove( model, options );
                }
        }
});

/**
 * A type of Backbone.Model that also maintains relations to other models and collections.
 * New events when compared to the original:
 *  - 'add:<key>' (model, related collection, options)
 *  - 'remove:<key>' (model, related collection, options)
 *  - 'change:<key>' (model, related model or collection, options)
 */
Backbone.RelationalModel = Backbone.Model.extend({
        relations: null, // Relation descriptions on the prototype
        _relations: null, // Relation instances
        _isInitialized: false,
        _deferProcessing: false,
        _queue: null,
        _attributeChangeFired: false, // Keeps track of `change` event firing under some conditions (like nested `set`s)

        subModelTypeAttribute: 'type',
        subModelTypes: null,

        constructor: function( attributes, options ) {
                // Nasty hack, for cases like 'model.get( <HasMany key> ).add( item )'.
                // Defer 'processQueue', so that when 'Relation.createModels' is used we trigger 'HasMany'
                // collection events only after the model is really fully set up.
                // Example: event for "p.on( 'add:jobs' )" -> "p.get('jobs').add( { company: c.id, person: p.id } )".
                if ( options && options.collection ) {
                        var dit = this,
                                collection = this.collection = options.collection;

                        // Prevent `collection` from cascading down to nested models; they shouldn't go into this `if` clause.
                        delete options.collection;

                        this._deferProcessing = true;

                        var processQueue = function( model ) {
                                if ( model === dit ) {
                                        dit._deferProcessing = false;
                                        dit.processQueue();
                                        collection.off( 'relational:add', processQueue );
                                }
                        };
                        collection.on( 'relational:add', processQueue );

                        // So we do process the queue eventually, regardless of whether this model actually gets added to 'options.collection'.
                        _.defer( function() {
                                processQueue( dit );
                        });
                }

                Backbone.Relational.store.processOrphanRelations();
                Backbone.Relational.store.listenTo( this, 'relational:unregister', Backbone.Relational.store.unregister );

                this._queue = new Backbone.BlockingQueue();
                this._queue.block();
                Backbone.Relational.eventQueue.block();

                try {
                        Backbone.Model.apply( this, arguments );
                }
                finally {
                        // Try to run the global queue holding external events
                        Backbone.Relational.eventQueue.unblock();
                }
        },

        /**
         * Override 'trigger' to queue 'change' and 'change:*' events
         */
        trigger: function( eventName ) {
                if ( eventName.length > 5 && eventName.indexOf( 'change' ) === 0 ) {
                        var dit = this,
                                args = arguments;

                        if ( !Backbone.Relational.eventQueue.isBlocked() ) {
                                // If we're not in a more complicated nested scenario, fire the change event right away
                                Backbone.Model.prototype.trigger.apply( dit, args );
                        }
                        else {
                                Backbone.Relational.eventQueue.add( function() {
                                        // Determine if the `change` event is still valid, now that all relations are populated
                                        var changed = true;
                                        if ( eventName === 'change' ) {
                                                // `hasChanged` may have gotten reset by nested calls to `set`.
                                                changed = dit.hasChanged() || dit._attributeChangeFired;
                                                dit._attributeChangeFired = false;
                                        }
                                        else {
                                                var attr = eventName.slice( 7 ),
                                                        rel = dit.getRelation( attr );

                                                if ( rel ) {
                                                        // If `attr` is a relation, `change:attr` get triggered from `Relation.onChange`.
                                                        // These take precedence over `change:attr` events triggered by `Model.set`.
                                                        // The relation sets a fourth attribute to `true`. If this attribute is present,
                                                        // continue triggering this event; otherwise, it's from `Model.set` and should be stopped.
                                                        changed = ( args[ 4 ] === true );

                                                        // If this event was triggered by a relation, set the right value in `this.changed`
                                                        // (a Collection or Model instead of raw data).
                                                        if ( changed ) {
                                                                dit.changed[ attr ] = args[ 2 ];
                                                        }
                                                        // Otherwise, this event is from `Model.set`. If the relation doesn't report a change,
                                                        // remove attr from `dit.changed` so `hasChanged` doesn't take it into account.
                                                        else if ( !rel.changed ) {
                                                                delete dit.changed[ attr ];
                                                        }
                                                }
                                                else if ( changed ) {
                                                        dit._attributeChangeFired = true;
                                                }
                                        }

                                        changed && Backbone.Model.prototype.trigger.apply( dit, args );
                                });
                        }
                }
                else if ( eventName === 'destroy' ) {
                        Backbone.Model.prototype.trigger.apply( this, arguments );
                        Backbone.Relational.store.unregister( this );
                }
                else {
                        Backbone.Model.prototype.trigger.apply( this, arguments );
                }

                return this;
        },

        /**
         * Initialize Relations present in this.relations; determine the type (HasOne/HasMany), then creates a new instance.
         * Invoked in the first call so 'set' (which is made from the Backbone.Model constructor).
         */
        initializeRelations: function( options ) {
                this.acquire(); // Setting up relations often also involve calls to 'set', and we only want to enter this function once
                this._relations = {};

                _.each( this.relations || [], function( rel ) {
                        Backbone.Relational.store.initializeRelation( this, rel, options );
                }, this );

                this._isInitialized = true;
                this.release();
                this.processQueue();
        },

        /**
         * When new values are set, notify this model's relations (also if options.silent is set).
         * (called from `set`; Relation.setRelated locks this model before calling 'set' on it to prevent loops)
         * @param {Object} [changedAttrs]
         * @param {Object} [options]
         */
        updateRelations: function( changedAttrs, options ) {
                if ( this._isInitialized && !this.isLocked() ) {
                        _.each( this._relations, function( rel ) {
                                if ( !changedAttrs || ( rel.keySource in changedAttrs || rel.key in changedAttrs ) ) {
                                        // Fetch data in `rel.keySource` if data got set in there, or `rel.key` otherwise
                                        var value = this.attributes[ rel.keySource ] || this.attributes[ rel.key ],
                                                attr = changedAttrs && ( changedAttrs[ rel.keySource ] || changedAttrs[ rel.key ] );

                                        // Update a relation if its value differs from this model's attributes, or it's been explicitly nullified.
                                        // Which can also happen before the originally intended related model has been found (`val` is null).
                                        if ( rel.related !== value || ( value === null && attr === null ) ) {
                                                this.trigger( 'relational:change:' + rel.key, this, value, options || {} );
                                        }
                                }

                                // Explicitly clear 'keySource', to prevent a leaky abstraction if 'keySource' differs from 'key'.
                                if ( rel.keySource !== rel.key ) {
                                        delete this.attributes[ rel.keySource ];
                                }
                        }, this );
                }
        },

        /**
         * Either add to the queue (if we're not initialized yet), or execute right away.
         */
        queue: function( func ) {
                this._queue.add( func );
        },

        /**
         * Process _queue
         */
        processQueue: function() {
                if ( this._isInitialized && !this._deferProcessing && this._queue.isBlocked() ) {
                        this._queue.unblock();
                }
        },

        /**
         * Get a specific relation.
         * @param {string} attr The relation key to look for.
         * @return {Backbone.Relation} An instance of 'Backbone.Relation', if a relation was found for 'attr', or null.
         */
        getRelation: function( attr ) {
                return this._relations[ attr ];
        },

        /**
         * Get all of the created relations.
         * @return {Backbone.Relation[]}
         */
        getRelations: function() {
                return _.values( this._relations );
        },

        /**
         * Get a list of ids that will be fetched on a call to `getAsync`.
         * @param {string|Backbone.Relation} attr The relation key to fetch models for.
         * @param [refresh=false] Add ids for models that are already in the relation, refreshing them?
         * @return {Array} An array of ids that need to be fetched.
         */
        getIdsToFetch: function( attr, refresh ) {
                var rel = attr instanceof Backbone.Relation ? attr : this.getRelation( attr ),
                        ids = rel ? ( rel.keyIds && rel.keyIds.slice( 0 ) ) || ( ( rel.keyId || rel.keyId === 0 ) ? [ rel.keyId ] : [] ) : [];

                // On `refresh`, add the ids for current models in the relation to `idsToFetch`
                if ( refresh ) {
                        var models = rel.related && ( rel.related.models || [ rel.related ] );
                        _.each( models, function( model ) {
                                if ( model.id || model.id === 0 ) {
                                        ids.push( model.id );
                                }
                        });
                }

                return ids;
        },

        /**
         * Get related objects. Returns a single promise, which can either resolve immediately (if the related model[s])
         * are already present locally, or after fetching the contents of the requested attribute.
         * @param {string} attr The relation key to fetch models for.
         * @param {Object} [options] Options for 'Backbone.Model.fetch' and 'Backbone.sync'.
         * @param {Boolean} [options.refresh=false] Fetch existing models from the server as well (in order to update them).
         * @return {jQuery.Deferred} A jQuery promise object. When resolved, its `done` callback will be called with
         *  contents of `attr`.
         */
        getAsync: function( attr, options ) {
                // Set default `options` for fetch
                options = _.extend( { add: true, remove: false, refresh: false }, options );

                var dit = this,
                        requests = [],
                        rel = this.getRelation( attr ),
                        idsToFetch = rel && this.getIdsToFetch( rel, options.refresh ),
                        coll = rel.related instanceof Backbone.Collection ? rel.related : rel.relatedCollection;

                if ( idsToFetch && idsToFetch.length ) {
                        var models = [],
                                createdModels = [],
                                setUrl,
                                createModels = function() {
                                        // Find (or create) a model for each one that is to be fetched
                                        models = _.map( idsToFetch, function( id ) {
                                                var model = rel.relatedModel.findModel( id );

                                                if ( !model ) {
                                                        var attrs = {};
                                                        attrs[ rel.relatedModel.prototype.idAttribute ] = id;
                                                        model = rel.relatedModel.findOrCreate( attrs, options );
                                                        createdModels.push( model );
                                                }

                                                return model;
                                        }, this );
                                };

                        // Try if the 'collection' can provide a url to fetch a set of models in one request.
                        // This assumes that when 'Backbone.Collection.url' is a function, it can handle building of set urls.
                        // To make sure it can, test if the url we got by supplying a list of models to fetch is different from
                        // the one supplied for the default fetch action (without args to 'url').
                        if ( coll instanceof Backbone.Collection && _.isFunction( coll.url ) ) {
                                var defaultUrl = coll.url();
                                setUrl = coll.url( idsToFetch );

                                if ( setUrl === defaultUrl ) {
                                        createModels();
                                        setUrl = coll.url( models );

                                        if ( setUrl === defaultUrl ) {
                                                setUrl = null;
                                        }
                                }
                        }

                        if ( setUrl ) {
                                // Do a single request to fetch all models
                                var opts = _.defaults(
                                        {
                                                error: function() {
                                                        _.each( createdModels, function( model ) {
                                                                model.trigger( 'destroy', model, model.collection, options );
                                                        });

                                                        options.error && options.error.apply( models, arguments );
                                                },
                                                url: setUrl
                                        },
                                        options
                                );

                                requests = [ coll.fetch( opts ) ];
                        }
                        else {
                                // Make a request per model to fetch
                                if  ( !models.length ) {
                                        createModels();
                                }

                                requests = _.map( models, function( model ) {
                                        var opts = _.defaults(
                                                {
                                                        error: function() {
                                                                if ( _.contains( createdModels, model ) ) {
                                                                        model.trigger( 'destroy', model, model.collection, options );
                                                                }
                                                                options.error && options.error.apply( models, arguments );
                                                        }
                                                },
                                                options
                                        );
                                        return model.fetch( opts );
                                }, this );
                        }
                }

                return this.deferArray(requests).then(
                        function() {
                                return Backbone.Model.prototype.get.call( dit, attr );
                        }
                );
        },

        deferArray: function(deferArray) {
                return Backbone.$.when.apply(null, deferArray);
        },

        set: function( key, value, options ) {
                Backbone.Relational.eventQueue.block();

                // Duplicate backbone's behavior to allow separate key/value parameters, instead of a single 'attributes' object
                var attributes,
                        result;

                if ( _.isObject( key ) || key == null ) {
                        attributes = key;
                        options = value;
                }
                else {
                        attributes = {};
                        attributes[ key ] = value;
                }

                try {
                        var id = this.id,
                                newId = attributes && this.idAttribute in attributes && attributes[ this.idAttribute ];

                        // Check if we're not setting a duplicate id before actually calling `set`.
                        Backbone.Relational.store.checkId( this, newId );

                        result = Backbone.Model.prototype.set.apply( this, arguments );

                        // Ideal place to set up relations, if this is the first time we're here for this model
                        if ( !this._isInitialized && !this.isLocked() ) {
                                this.constructor.initializeModelHierarchy();

                                // Only register models that have an id. A model will be registered when/if it gets an id later on.
                                if ( newId || newId === 0 ) {
                                        Backbone.Relational.store.register( this );
                                }

                                this.initializeRelations( options );
                        }
                        // The store should know about an `id` update asap
                        else if ( newId && newId !== id ) {
                                Backbone.Relational.store.update( this );
                        }

                        if ( attributes ) {
                                this.updateRelations( attributes, options );
                        }
                }
                finally {
                        // Try to run the global queue holding external events
                        Backbone.Relational.eventQueue.unblock();
                }

                return result;
        },

        clone: function() {
                var attributes = _.clone( this.attributes );
                if ( !_.isUndefined( attributes[ this.idAttribute ] ) ) {
                        attributes[ this.idAttribute ] = null;
                }

                _.each( this.getRelations(), function( rel ) {
                        delete attributes[ rel.key ];
                });

                return new this.constructor( attributes );
        },

        /**
         * Convert relations to JSON, omits them when required
         */
        toJSON: function( options ) {
                // If this Model has already been fully serialized in this branch once, return to avoid loops
                if ( this.isLocked() ) {
                        return this.id;
                }

                this.acquire();
                var json = Backbone.Model.prototype.toJSON.call( this, options );

                if ( this.constructor._superModel && !( this.constructor._subModelTypeAttribute in json ) ) {
                        json[ this.constructor._subModelTypeAttribute ] = this.constructor._subModelTypeValue;
                }

                _.each( this._relations, function( rel ) {
                        var related = json[ rel.key ],
                                includeInJSON = rel.options.includeInJSON,
                                value = null;

                        if ( includeInJSON === true ) {
                                if ( related && _.isFunction( related.toJSON ) ) {
                                        value = related.toJSON( options );
                                }
                        }
                        else if ( _.isString( includeInJSON ) ) {
                                if ( related instanceof Backbone.Collection ) {
                                        value = related.pluck( includeInJSON );
                                }
                                else if ( related instanceof Backbone.Model ) {
                                        value = related.get( includeInJSON );
                                }

                                // Add ids for 'unfound' models if includeInJSON is equal to (only) the relatedModel's `idAttribute`
                                if ( includeInJSON === rel.relatedModel.prototype.idAttribute ) {
                                        if ( rel instanceof Backbone.HasMany ) {
                                                value = value.concat( rel.keyIds );
                                        }
                                        else if ( rel instanceof Backbone.HasOne ) {
                                                value = value || rel.keyId;

                                                if ( !value && !_.isObject( rel.keyContents ) ) {
                                                        value = rel.keyContents || null;
                                                }
                                        }
                                }
                        }
                        else if ( _.isArray( includeInJSON ) ) {
                                if ( related instanceof Backbone.Collection ) {
                                        value = [];
                                        related.each( function( model ) {
                                                var curJson = {};
                                                _.each( includeInJSON, function( key ) {
                                                        curJson[ key ] = model.get( key );
                                                });
                                                value.push( curJson );
                                        });
                                }
                                else if ( related instanceof Backbone.Model ) {
                                        value = {};
                                        _.each( includeInJSON, function( key ) {
                                                value[ key ] = related.get( key );
                                        });
                                }
                        }
                        else {
                                delete json[ rel.key ];
                        }

                        // In case of `wait: true`, Backbone will simply push whatever's passed into `save` into attributes.
                        // We'll want to get this information into the JSON, even if it doesn't conform to our normal
                        // expectations of what's contained in it (no model/collection for a relation, etc).
                        if ( value === null && options && options.wait ) {
                                value = related;
                        }

                        if ( includeInJSON ) {
                                json[ rel.keyDestination ] = value;
                        }

                        if ( rel.keyDestination !== rel.key ) {
                                delete json[ rel.key ];
                        }
                });

                this.release();
                return json;
        }
},
{
        /**
         *
         * @param superModel
         * @returns {Backbone.RelationalModel.constructor}
         */
        setup: function( superModel ) {
                // We don't want to share a relations array with a parent, as this will cause problems with reverse
                // relations. Since `relations` may also be a property or function, only use slice if we have an array.
                this.prototype.relations = ( this.prototype.relations || [] ).slice( 0 );

                this._subModels = {};
                this._superModel = null;

                // If this model has 'subModelTypes' itself, remember them in the store
                if ( this.prototype.hasOwnProperty( 'subModelTypes' ) ) {
                        Backbone.Relational.store.addSubModels( this.prototype.subModelTypes, this );
                }
                // The 'subModelTypes' property should not be inherited, so reset it.
                else {
                        this.prototype.subModelTypes = null;
                }

                // Initialize all reverseRelations that belong to this new model.
                _.each( this.prototype.relations || [], function( rel ) {
                        if ( !rel.model ) {
                                rel.model = this;
                        }

                        if ( rel.reverseRelation && rel.model === this ) {
                                var preInitialize = true;
                                if ( _.isString( rel.relatedModel ) ) {
                                        /**
                                         * The related model might not be defined for two reasons
                                         *  1. it is related to itself
                                         *  2. it never gets defined, e.g. a typo
                                         *  3. the model hasn't been defined yet, but will be later
                                         * In neither of these cases do we need to pre-initialize reverse relations.
                                         * However, for 3. (which is, to us, indistinguishable from 2.), we do need to attempt
                                         * setting up this relation again later, in case the related model is defined later.
                                         */
                                        var relatedModel = Backbone.Relational.store.getObjectByName( rel.relatedModel );
                                        preInitialize = relatedModel && ( relatedModel.prototype instanceof Backbone.RelationalModel );
                                }

                                if ( preInitialize ) {
                                        Backbone.Relational.store.initializeRelation( null, rel );
                                }
                                else if ( _.isString( rel.relatedModel ) ) {
                                        Backbone.Relational.store.addOrphanRelation( rel );
                                }
                        }
                }, this );

                return this;
        },

        /**
         * Create a 'Backbone.Model' instance based on 'attributes'.
         * @param {Object} attributes
         * @param {Object} [options]
         * @return {Backbone.Model}
         */
        build: function( attributes, options ) {
                // 'build' is a possible entrypoint; it's possible no model hierarchy has been determined yet.
                this.initializeModelHierarchy();

                // Determine what type of (sub)model should be built if applicable.
                var model = this._findSubModelType( this, attributes ) || this;

                return new model( attributes, options );
        },

        /**
         * Determines what type of (sub)model should be built if applicable.
         * Looks up the proper subModelType in 'this._subModels', recursing into
         * types until a match is found.  Returns the applicable 'Backbone.Model'
         * or null if no match is found.
         * @param {Backbone.Model} type
         * @param {Object} attributes
         * @return {Backbone.Model}
         */
        _findSubModelType: function( type, attributes ) {
                if ( type._subModels && type.prototype.subModelTypeAttribute in attributes ) {
                        var subModelTypeAttribute = attributes[ type.prototype.subModelTypeAttribute ];
                        var subModelType = type._subModels[ subModelTypeAttribute ];
                        if ( subModelType ) {
                                return subModelType;
                        }
                        else {
                                // Recurse into subModelTypes to find a match
                                for ( subModelTypeAttribute in type._subModels ) {
                                        subModelType = this._findSubModelType( type._subModels[ subModelTypeAttribute ], attributes );
                                        if ( subModelType ) {
                                                return subModelType;
                                        }
                                }
                        }
                }

                return null;
        },

        /**
         *
         */
        initializeModelHierarchy: function() {
                // Inherit any relations that have been defined in the parent model.
                this.inheritRelations();

                // If we came here through 'build' for a model that has 'subModelTypes' then try to initialize the ones that
                // haven't been resolved yet.
                if ( this.prototype.subModelTypes ) {
                        var resolvedSubModels = _.keys( this._subModels );
                        var unresolvedSubModels = _.omit( this.prototype.subModelTypes, resolvedSubModels );
                        _.each( unresolvedSubModels, function( subModelTypeName ) {
                                var subModelType = Backbone.Relational.store.getObjectByName( subModelTypeName );
                                subModelType && subModelType.initializeModelHierarchy();
                        });
                }
        },

        inheritRelations: function() {
                // Bail out if we've been here before.
                if ( !_.isUndefined( this._superModel ) && !_.isNull( this._superModel ) ) {
                        return;
                }
                // Try to initialize the _superModel.
                Backbone.Relational.store.setupSuperModel( this );

                // If a superModel has been found, copy relations from the _superModel if they haven't been inherited automatically
                // (due to a redefinition of 'relations').
                if ( this._superModel ) {
                        // The _superModel needs a chance to initialize its own inherited relations before we attempt to inherit relations
                        // from the _superModel. You don't want to call 'initializeModelHierarchy' because that could cause sub-models of
                        // this class to inherit their relations before this class has had chance to inherit it's relations.
                        this._superModel.inheritRelations();
                        if ( this._superModel.prototype.relations ) {
                                // Find relations that exist on the '_superModel', but not yet on this model.
                                var inheritedRelations = _.filter( this._superModel.prototype.relations || [], function( superRel ) {
                                        return !_.any( this.prototype.relations || [], function( rel ) {
                                                return superRel.relatedModel === rel.relatedModel && superRel.key === rel.key;
                                        }, this );
                                }, this );

                                this.prototype.relations = inheritedRelations.concat( this.prototype.relations );
                        }
                }
                // Otherwise, make sure we don't get here again for this type by making '_superModel' false so we fail the
                // isUndefined/isNull check next time.
                else {
                        this._superModel = false;
                }
        },

        /**
         * Find an instance of `this` type in 'Backbone.Relational.store'.
         * A new model is created if no matching model is found, `attributes` is an object, and `options.create` is true.
         * - If `attributes` is a string or a number, `findOrCreate` will query the `store` and return a model if found.
         * - If `attributes` is an object and is found in the store, the model will be updated with `attributes` unless `options.merge` is `false`.
         * @param {Object|String|Number} attributes Either a model's id, or the attributes used to create or update a model.
         * @param {Object} [options]
         * @param {Boolean} [options.create=true]
         * @param {Boolean} [options.merge=true]
         * @param {Boolean} [options.parse=false]
         * @return {Backbone.RelationalModel}
         */
        findOrCreate: function( attributes, options ) {
                options || ( options = {} );
                var parsedAttributes = ( _.isObject( attributes ) && options.parse && this.prototype.parse ) ?
                        this.prototype.parse( _.clone( attributes ), options ) : attributes;

                // If specified, use a custom `find` function to match up existing models to the given attributes.
                // Otherwise, try to find an instance of 'this' model type in the store
                var model = this.findModel( parsedAttributes );

                // If we found an instance, update it with the data in 'item' (unless 'options.merge' is false).
                // If not, create an instance (unless 'options.create' is false).
                if ( _.isObject( attributes ) ) {
                        if ( model && options.merge !== false ) {
                                // Make sure `options.collection` and `options.url` doesn't cascade to nested models
                                delete options.collection;
                                delete options.url;

                                model.set( parsedAttributes, options );
                        }
                        else if ( !model && options.create !== false ) {
                                model = this.build( parsedAttributes, _.defaults( { parse: false }, options ) );
                        }
                }

                return model;
        },

        /**
         * Find an instance of `this` type in 'Backbone.Relational.store'.
         * - If `attributes` is a string or a number, `find` will query the `store` and return a model if found.
         * - If `attributes` is an object and is found in the store, the model will be updated with `attributes` unless `options.merge` is `false`.
         * @param {Object|String|Number} attributes Either a model's id, or the attributes used to create or update a model.
         * @param {Object} [options]
         * @param {Boolean} [options.merge=true]
         * @param {Boolean} [options.parse=false]
         * @return {Backbone.RelationalModel}
         */
        find: function( attributes, options ) {
                options || ( options = {} );
                options.create = false;
                return this.findOrCreate( attributes, options );
        },

        /**
         * A hook to override the matching when updating (or creating) a model.
         * The default implementation is to look up the model by id in the store.
         * @param {Object} attributes
         * @returns {Backbone.RelationalModel}
         */
        findModel: function( attributes ) {
                return Backbone.Relational.store.find( this, attributes );
        }
});
_.extend( Backbone.RelationalModel.prototype, Backbone.Semaphore );

/**
 * Override Backbone.Collection._prepareModel, so objects will be built using the correct type
 * if the collection.model has subModels.
 * Attempts to find a model for `attrs` in Backbone.store through `findOrCreate`
 * (which sets the new properties on it if found), or instantiates a new model.
 */
Backbone.Collection.prototype.__prepareModel = Backbone.Collection.prototype._prepareModel;
Backbone.Collection.prototype._prepareModel = function( attrs, options ) {
        var model;

        if ( attrs instanceof Backbone.Model ) {
                if ( !attrs.collection ) {
                        attrs.collection = this;
                }
                model = attrs;
        }
        else {
                options = options ? _.clone( options ) : {};
                options.collection = this;

                if ( typeof this.model.findOrCreate !== 'undefined' ) {
                        model = this.model.findOrCreate( attrs, options );
                }
                else {
                        model = new this.model( attrs, options );
                }

                if ( model && model.validationError ) {
                        this.trigger( 'invalid', this, attrs, options );
                        model = false;
                }
        }

        return model;
};

/**
 * Override Backbone.Collection.set, so we'll create objects from attributes where required,
 * and update the existing models. Also, trigger 'relational:add'.
 */
var set = Backbone.Collection.prototype.__set = Backbone.Collection.prototype.set;
Backbone.Collection.prototype.set = function( models, options ) {
        // Short-circuit if this Collection doesn't hold RelationalModels
        if ( !( this.model.prototype instanceof Backbone.RelationalModel ) ) {
                return set.call( this, models, options );
        }

        if ( options && options.parse ) {
                models = this.parse( models, options );
        }

        var singular = !_.isArray( models ),
                newModels = [],
                toAdd = [],
                model = null;

        models = singular ? ( models ? [ models ] : [] ) : _.clone( models );

        //console.debug( 'calling add on coll=%o; model=%o, options=%o', this, models, options );
        for ( var i = 0; i < models.length; i++ ) {
                model = models[i];
                if ( !( model instanceof Backbone.Model ) ) {
                        model = Backbone.Collection.prototype._prepareModel.call( this, model, options );
                }
                if ( model ) {
                        toAdd.push( model );
                        if ( !( this.get( model ) || this.get( model.cid ) ) ) {
                                newModels.push( model );
                        }
                        // If we arrive in `add` while performing a `set` (after a create, so the model gains an `id`),
                        // we may get here before `_onModelEvent` has had the chance to update `_byId`.
                        else if ( model.id !== null && model.id !== undefined ) {
                                this._byId[ model.id ] = model;
                        }
                }
        }

        // Add 'models' in a single batch, so the original add will only be called once (and thus 'sort', etc).
        // If `parse` was specified, the collection and contained models have been parsed now.
        toAdd = singular ? ( toAdd.length ? toAdd[ 0 ] : null ) : toAdd;
        var result = set.call( this, toAdd, _.defaults( { merge: false, parse: false }, options ) );

        for ( i = 0; i < newModels.length; i++ ) {
                model = newModels[i];
                // Fire a `relational:add` event for any model in `newModels` that has actually been added to the collection.
                if ( this.get( model ) || this.get( model.cid ) ) {
                        this.trigger( 'relational:add', model, this, options );
                }
        }

        return result;
};

/**
 * Override 'Backbone.Collection._removeModels' to trigger 'relational:remove'.
 */
var _removeModels = Backbone.Collection.prototype.___removeModels = Backbone.Collection.prototype._removeModels;
Backbone.Collection.prototype._removeModels = function( models, options ) {
        // Short-circuit if this Collection doesn't hold RelationalModels
        if ( !( this.model.prototype instanceof Backbone.RelationalModel ) ) {
                return _removeModels.call( this, models, options );
        }

        var toRemove = [];

        //console.debug('calling remove on coll=%o; models=%o, options=%o', this, models, options );
        _.each( models, function( model ) {
                model = this.get( model ) || ( model && this.get( model.cid ) );
                model && toRemove.push( model );
        }, this );

        var result = _removeModels.call( this, toRemove, options );

        _.each( toRemove, function( model ) {
                this.trigger( 'relational:remove', model, this, options );
        }, this );

        return result;
};

/**
 * Override 'Backbone.Collection.reset' to trigger 'relational:reset'.
 */
var reset = Backbone.Collection.prototype.__reset = Backbone.Collection.prototype.reset;
Backbone.Collection.prototype.reset = function( models, options ) {
        options = _.extend( { merge: true }, options );
        var result = reset.call( this, models, options );

        if ( this.model.prototype instanceof Backbone.RelationalModel ) {
                this.trigger( 'relational:reset', this, options );
        }

        return result;
};

/**
 * Override 'Backbone.Collection.sort' to trigger 'relational:reset'.
 */
var sort = Backbone.Collection.prototype.__sort = Backbone.Collection.prototype.sort;
Backbone.Collection.prototype.sort = function( options ) {
        var result = sort.call( this, options );

        if ( this.model.prototype instanceof Backbone.RelationalModel ) {
                this.trigger( 'relational:reset', this, options );
        }

        return result;
};

/**
 * Override 'Backbone.Collection.trigger' so 'add', 'remove' and 'reset' events are queued until relations
 * are ready.
 */
var trigger = Backbone.Collection.prototype.__trigger = Backbone.Collection.prototype.trigger;
Backbone.Collection.prototype.trigger = function( eventName ) {
        // Short-circuit if this Collection doesn't hold RelationalModels
        if ( !( this.model.prototype instanceof Backbone.RelationalModel ) ) {
                return trigger.apply( this, arguments );
        }

        if ( eventName === 'add' || eventName === 'remove' || eventName === 'reset' || eventName === 'sort' ) {
                var dit = this,
                        args = arguments;

                if ( _.isObject( args[ 3 ] ) ) {
                        args = _.toArray( args );
                        // the fourth argument is the option object.
                        // we need to clone it, as it could be modified while we wait on the eventQueue to be unblocked
                        args[ 3 ] = _.clone( args[ 3 ] );
                }

                Backbone.Relational.eventQueue.add( function() {
                        trigger.apply( dit, args );
                });
        }
        else {
                trigger.apply( this, arguments );
        }

        return this;
};

// Override .extend() to automatically call .setup()
Backbone.RelationalModel.extend = function( protoProps, classProps ) {
        var child = Backbone.Model.extend.call( this, protoProps, classProps );

        child.setup( this );

        return child;
};

}));